In the United States alone, approximately 14 million people suffer from some form of Chronic Obstructive Pulmonary Disease (COPD). However an additional ten million adults have evidence of impaired lung function indicating that COPD may be significantly underdiagnosed. The cost of COPD to the nation in 2002 was estimated to be $32.1 billion. Medicare expenses for COPD beneficiaries were nearly 2.5 times that of the expenditures for all other patients. Direct medical services accounted for $18.0 billion, and indirect cost of morbidity and premature mortality was $14.1 billion. COPD is the fourth leading cause of death in the U.S. and is projected to be the third leading cause of death for both males and females by the year 2020.
Chronic Obstructive Pulmonary Disease (COPD) is a progressive disease of the airways that is characterized by a gradual loss of lung function. In the United States, the term COPD includes chronic bronchitis, chronic obstructive bronchitis, and emphysema, or combinations of these conditions. In emphysema the alveoli walls of the lung tissue are progressively weakened and lose their elastic recoil. The breakdown of lung tissue causes progressive loss of elastic recoil and the loss of radial support of the airways which traps residual air in the lung. This increases the work of exhaling and leads to hyperinflation of the lung. When the lungs become hyperinflated, forced expiration cannot reduce the residual volume of the lungs because the force exerted to empty the lungs collapses the small airways and blocks air from being exhaled. As the disease progresses, the inspiratory capacity and air exchange surface area of the lungs is reduced until air exchange becomes seriously impaired and the individual can only take short shallow labored breaths (dyspnea).
The symptoms of COPD can range from the chronic cough and sputum production of chronic bronchitis to the severe disabling shortness of breath of emphysema. In some individuals, chronic cough and sputum production are the first signs that they are at risk for developing the airflow obstruction and shortness of breath characteristic of COPD. With continued exposure to cigarettes or noxious particles, the disease progresses and individuals with COPD increasingly lose their ability to breathe. Acute infections or certain weather conditions may temporarily worsen symptoms (exacerbations), occasionally where hospitalization may be required. In others, shortness of breath may be the first indication of the disease. The diagnosis of COPD is confirmed by the presence of airway obstruction on testing with spirometry. Ultimately, severe emphysema may lead to severe dyspnea, severe limitation of daily activities, illness and death.
There is no cure for COPD or pulmonary emphysema, only various treatments for ameliorating the symptoms. The goal of current treatments is to help people live with the disease more comfortably and to prevent the progression of the disease. The current options include: self-care (e.g., quitting smoking), therapeutic agents (such as bronchodilators which do not address emphysema physiology), long-term oxygen therapy, and surgery (lung transplantation and lung volume reduction surgery). Lung Volume Reduction Surgery (LVRS) is an invasive procedure primarily for patients who have a localized (heterogeneous) version of emphysema; in which, the most diseased area of the lung is surgically removed to allow the remaining tissue to work more efficiently. Patients with diffuse emphysema cannot be treated with LVRS, and typically only have lung transplantation as an end-stage option. However, many patients are not candidates for such a taxing procedure.
A number of less-invasive surgical methods have been proposed for ameliorating the symptoms of COPD. In one approach new windows are opened inside the lung to allow air to more easily escape from the diseased tissue into the natural airways. These windows are kept open with permanently implanted stents. Other approaches attempt to seal off and shrink portions of the hyperinflated lung using chemical treatments and/or implantable plugs. However, these proposals remain significantly invasive and are still in clinical trails. None of the surgical approaches to treatment of COPD has been widely adopted. Therefore, a large unmet need remains for a medical procedure that can sufficiently alleviate the debilitating effects of COPD and emphysema and is accepted by physicians and patients.
Additionally, respiratory diseases like asthma and COPD are typically treated with inhaled therapeutic agents in order to relieve bronchoconstriction and inflammation in the lung tissue. There are several advantages to administering these therapeutic agents via the inhaled route compared to oral therapy including for example, a faster onset of action, lower therapeutic agent doses and a better efficacy to-safety ratio. therapeutic agent delivery by inhalation is also painless and is more convenient than injectable therapeutic agents and thus patient acceptance and compliance is more likely. However, delivery of therapeutic agents into lung tissue is difficult in asthma and COPD treatment because some patients cannot take the deep breathe necessary to inhale an therapeutic agent aerosol or therapeutic agent powder deep into the lung. Also many of the inhaler device are difficult to operate. Significant and variable amounts of the therapeutic agent are filtered and/or absorbed in the upper respiratory tract. Thus inhaled therapeutic agent delivery is difficult of impossible in the very patients that would benefit most.